That offering is crème de marrons de l'Ardèche (sweet chestnut purée from the Ardèche), invented by company founder Clément Faugier. Faugier first set up a chestnut-based foods factory in the small village of Privas, in central France in 1882. What started out as a family business with a dozen employees has grown into one of France's most respected food brands with exports to over 80 countries.

For the first three years, the factory made marrons glacés, or candied chestnuts, a popular delicacy in France. Trying to find a way to recycle the “debris” from these sweets, Faugier created his own recipe for crème de marrons. The factory has been churning out the stuff ever since and it has become a popular food, eaten with yogurt, ice cream and many other sweets throughout France. Today, Clément Faugier's crème de marrons holds a monopoly in that food category with an 80 percent market share in France.

Chefs swear by it, children love it for its richness and sweetness, and adults feel affection for it because Marono, the company mascot who resembles a spiky chestnut equivalent of the Michelin man, reminds them of their childhood. How did this small family run business grow to become one of France's most cherished food brands?

Unsurprisingly, company director Claude Boiron, believes that the food sells so well simply because it's so “unique and delicious.” "It's a good product," he says. "We've been making it for 120 years. The recipe is exactly the same today as when we first sold it, and so are the ingredients. So if the French like the crème de marrons, it is because of Clément Faugier. People have tried to copy us, but they don't have the right ingredients. When consumers have opted for something else, they then come running back to us because they just can't find the taste anywhere else."

The truth is that the brand's crème de marrons is the only version for sale in most food stores and supermarkets nationwide. The closest alternative is chestnut jam, but Clément Faugier still sells six times more crème de marrons than Andros -- one of France's largest jam manufacturers -- sells chestnut jam, despite the fact that Clément Faugier’s product is more expensive.

The reason this brand of crème de marrons has entered gastronomic legend might be because of its old fashioned simplicity; what you see is what you get. Crème de marrons is made from 100 percent natural ingredients: chestnuts, vanilla, sugar and water. The packaging, which Boiron "wouldn't change for the world," also plays in important part in the product's appeal. The brown and white tins, labeled with the company name written in an old-fashioned font and the company mascot, a chestnut with a smiling face, have not changed at all since they were first designed in 1938. The earthy colors are comforting, and the old-fashioned design hints of traditional, natural foods dating from a bygone era.

"If you ask someone if they know crème de marrons, they might not know which brand they are buying. But if you show them the tin, they will say 'oh yes, it's this one'. It's the packaging, which means there is a lot of impulse buying in the shops," adds Boiron. French families recognize the brand because their mothers and grandmothers bought it.

"The best crème de marrons is Clément Faugier," said a Spanish crêpe seller on a Paris street corner, as he spread a thick coating of the stuff on a pancake. (Pancakes with crème de marrons are a common snack in France.) "But you can also eat it with other things like whipped cream. It's delicious," he adds.

No one knows exactly what makes crème de marrons so delicious. Clément Faugier is a very secretive company; it never advertises, and keeps recipes and figures tucked tightly within the bosom of the company. "Live happily, live quietly" is Boiron's motto with which he justifies the company's silence on these matters. He explains consumer loyalty simply by the fact that customers have become used to the taste of the company's recipe, and will not settle for anything else.

"The consumer's palate has grown accustomed to our product. Our secret has been protected all these years, and our colleagues just don't have the same ingredients we do," said Boiron. He believes consumers are loyal to the brand because they think it makes the best sweet chestnut purée around -- a differentiator that ensures Clément Faugier can corner the market.

For the French, it seems to be as simple as that.

Emilie Boyer King is a freelance journalist specializing in French topics for major dailies and magazines around the world. She lives in Paris where she previously worked for BusinessWeek, Bloomberg News and the International Herald Tribune.